On the basis of the dredging process of coral reef fragments of the solid-liquid two-phase flow movement in the horizontal pipe,a numerical analysis model of fluid solid coupling about coral reef pipeline transportation is established.The dynamic characteristics of coral reef solid fragments on the horizontal pipeline are analyzed in detail including the coral reef density,particle size and slurry concentration.The results show that the smaller density of coral reef,the smaller particle size and the bigger slurry concentration can cause a smaller particles critical velocity；on the contrary,the bigger coral fragments density,larger particle size and the smaller slurry concentration can lead to a bigger critical velocity of coral reef fragments in the horizontal pipeline.Based on the numerical results,a new formula about the critical velocity of coral reef is proposed,which is verified with the numerical results.It is found that the formula proposed can be used to predict the critical velocity of coral reef in horizontal pipeline with an average error less than 15%.